Recently, a technique known as OpenFlow has been proposed, see Non-Patent Literatures 1, 2. The OpenFlow comprehends communication as an end-to-end flow and manages path control, recovery from malfunctions, load balancing and optimization from one flow to another. An OpenFlow switch, specified in Non-Patent Literature 2, includes a secure channel over which to communicate with an OpenFlow Controller, and operates in accordance with a flow table an addition to or a rewriting in which is instructed as necessary from the OpenFlow Controller. In the flow table, a set of match conditions (Match Fields) for matching against a packet header, the flow statistics information (Counters) and a set of instructions that define the processing contents (Instructions) are defined from one flow to another. See ‘4.1 Flow Table’ of Non-Patent Literature 2.
On reception of a packet, the OpenFlow switch searches the flow table for an entry having the match condition conforming to the header information of the received packet. See ‘4.4 Matching’ of Non-Patent Literature 2. If, as a result of the search, the entry matching the received packet is found, the OpenFlow switch updates the flow statistics information (Counters), at the same time as it executes processing contents stated in the instruction field of the matching entry, such as transmission at a specified port, flooding or dropping. If conversely no entry matching the received packet is found, the OpenFlow switch sends an entry setting request, that is, a request for having the control information sent to it in order to process the received packet (Packet-In message), to the OpenFlow Controller over the secure channel. The OpenFlow switch receives the flow entry, in which processing contents are stated, and accordingly updates its flow table. In this manner, the OpenFlow switch forwards the packet, using the entry stored in the flow table as the control information.
In Non-Patent Literature 1, there is disclosed a method for leasing a redundant path that is not in use in an optical network system. Specifically, a setting controller of the optical network system recruits candidate users and decides the amounts of lease fees or the amount of the resources leased in dependence upon the number of the candidate users.